1. Field of the Invention
The present invention relates to a pointing stick device, and more particularly, to a pointing stick device with increased sensitivity in the vertical direction.
2. Description of the Prior Art
Pointing devices, such as keyboards, mice, joysticks and remote control devices, are widely used computer peripherals for controlling the movement, position and function of a cursor on a computer screen. The prior art pointing device can only control the two-dimensional movement of the cursor. This means that, after moving the cursor to the desired position, another button must be clicked to execute the desired function. Moreover, as 3-D pictures and 3-D animations become more widespread, a pointing device that can generate three-dimensional, rather than two-dimensional, signals will prove more convenient for users when controlling movements in a 3-D space.
Please refer to FIG. 1. FIG. 1 is a cross-sectional diagram of a prior art pointing stick device 10. The prior art pointing stick device 10 comprises a column-shaped stick 12 for controlling the two-dimensional movements of a cursor (not shown) on a computer screen. The stick 12 has an upper portion 13 and a lower portion 15. The pointing stick device 10 further comprises a base plate 20 having an aperture 21 for fixing the stick 12, a plurality of strain gauges 14 vertically installed on the lower portion 15 of the stick 12, and a binding compound 22 filling the space between the lower portion 15 of the stick 12 and the aperture 21 of the base plate 20. The strain gauges 14 sense pressure and generate corresponding sensing signals. The binding compound 22 fixes the lower portion 15 of the stick 12 vertically into the aperture 21 of the base plate 20.
Please refer to FIG. 2. FIG. 2 is a cross-sectional diagram of another prior art pointing stick device 30. The main difference between the pointing stick device 30 and the pointing stick device 10 is that the pointing device 30 has a cover ring 26 installed on the periphery of the binding compound 22. When the stick is bent by a horizontal force, the cover ring 26 will help generate the reaction forces that squeeze the plurality of strain gauges 14 installed on the stick 12, and thereby cause the strain gauges 14 to generate the corresponding signals.
Please refer to FIG. 3 and FIG. 4. FIG. 3 is a cross-sectional diagram of the pointing stick device 10 or 30 shown in FIG. 1 or FIG. 2 with a horizontal force acting on the stick 12. The central line shown in FIG. 3 represents the bending direction of the stick 12 with the horizontal force. The bending of the stick 12 caused by the horizontal force will make the strain gauge 14 generate bending strain signals Sx1, Sy1. FIG. 4 is a cross-sectional diagram of the pointing stick device 10 or 30 shown in FIG. 1 or FIG. 2 with a vertical force acting on the stick 12. The central line shown in FIG. 4 represents the direction of compression of the stick 12 with the vertical force. The compression of the stick 12 caused by the vertical force will make the strain gauge 14 generate compressive strain signals Sz1) When a force is applied to the pointing stick device 10, 30, the base plate 20 and the binding compound 22 will squeeze the strain gauges which then generate the strain signals Sx1, Sy1, and Sz1. 
However, the upper and lower portions 13, 15 of the stick 12 of the prior art pointing stick devices 10, 30 are of a vertical, columnar shape, as is the corresponding aperture 21 of the base plate 20. Thus, when a force is applied to the pointing stick device 10, 30, the strain signals Sz1 in the Z direction are too insignificant to use. Although, in the pointing stick device 30, there is the cover ring 26 installed on the lower portion 15 of the stick 12, it still cannot intensify the strain signals Sz1 in the Z direction. Furthermore, adding the cover ring 26 on the prior art pointing stick device 30 requires additional materials, gluing and working hours, raising production costs. Accordingly, how to design a pointing stick device with increased sensitivity in the X, Y (horizontal) and Z (vertical) directions becomes the goal for a designer to strive for.
It is therefore a primary objective of the present invention to provide a pointing stick device with increased sensitivity in the vertical direction to solve the above mentioned problems.
In a preferred embodiment, the present invention provides a pointing stick device for use with a computer. The pointing stick device comprises:
a base plate having an aperture;
a stick having an upper portion, and a lower portion with a tapering section;
at least one strain gauge installed on the lower portion for sensing pressure and generating corresponding sensing signals; and
a binding compound filling the space between a periphery of the lower portion of the stick and the aperture of the base plate and covering the strain gauge, for fixing the lower portion of the stick vertically in the aperture of the base plate;
wherein when the stick is vertically depressed, the strain gauge installed on the periphery of the lower portion of the stick can sense vertical downward pressure from reaction forces transmitted through the binding compound and generate the corresponding sensing signals.
It is an advantage of the present invention that the pointing stick device can increase the strain gauge sensitivity, especially in the vertical direction.
These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.